35 research outputs found
Random Access Scheduling without Message Passing: A Collision-based AIMD Approach
Department of Computer EngineeringWireless scheduling has been extensively studied in the literature. Since Maximum Weighted Scheduling has been developed and shown to achieve the optimal performance, there have been many efforts to overcome its complexity issue. Random access has attracted much attention due to its potential for low complexity and distributed control, which are desirable for scheduling in multi-hop wireless networks. Although several interesting random access scheduling schemes have been shown to be provably efficient, they suffer in practice from high packet delays or severe performance degradation due to the control overhead to exchange information between neighboring links. In this paper, we develop a novel random access scheduling scheme that does not need message passing. We pay attention to the interplay between the links and control their access probabilities targeting at a certain collision rate. We employ the Additive Increase Multiplicative Decrease (AIMD) algorithm for convergence, and show that our proposed scheme can achieve the same performance bound as the previous random access schemes with high control overhead. We verify our results through simulations and show that our proposed scheme achieves the performance close to that of the centralized greedy algorithm.ope
Exploiting Regional Differences: A Spatially Adaptive Random Access
In this paper, we discuss the potential for improvement of the simple random
access scheme by utilizing local information such as the received
signal-to-interference-plus-noise-ratio (SINR). We propose a spatially adaptive
random access (SARA) scheme in which the transmitters in the network utilize
different transmit probabilities depending on the local situation. In our
proposed scheme, the transmit probability is adaptively updated by the ratio of
the received SINR and the target SINR. We investigate the performance of the
spatially adaptive random access scheme. For the comparison, we derive an
optimal transmit probability of ALOHA random access scheme in which all
transmitters use the same transmit probability. We illustrate the performance
of the spatially adaptive random access scheme through simulations. We show
that the performance of the proposed scheme surpasses that of the optimal ALOHA
random access scheme and is comparable with the CSMA/CA scheme.Comment: 10 pages, 10 figure
Embedding of Virtual Network Requests over Static Wireless Multihop Networks
Network virtualization is a technology of running multiple heterogeneous
network architecture on a shared substrate network. One of the crucial
components in network virtualization is virtual network embedding, which
provides a way to allocate physical network resources (CPU and link bandwidth)
to virtual network requests. Despite significant research efforts on virtual
network embedding in wired and cellular networks, little attention has been
paid to that in wireless multi-hop networks, which is becoming more important
due to its rapid growth and the need to share these networks among different
business sectors and users. In this paper, we first study the root causes of
new challenges of virtual network embedding in wireless multi-hop networks, and
propose a new embedding algorithm that efficiently uses the resources of the
physical substrate network. We examine our algorithm's performance through
extensive simulations under various scenarios. Due to lack of competitive
algorithms, we compare the proposed algorithm to five other algorithms, mainly
borrowed from wired embedding or artificially made by us, partially with or
without the key algorithmic ideas to assess their impacts.Comment: 22 page
Cognitive MAC Protocols Using Memory for Distributed Spectrum Sharing Under Limited Spectrum Sensing
The main challenges of cognitive radio include spectrum sensing at the
physical (PHY) layer to detect the activity of primary users and spectrum
sharing at the medium access control (MAC) layer to coordinate access among
coexisting secondary users. In this paper, we consider a cognitive radio
network in which a primary user shares a channel with secondary users that
cannot distinguish the signals of the primary user from those of a secondary
user. We propose a class of distributed cognitive MAC protocols to achieve
efficient spectrum sharing among the secondary users while protecting the
primary user from potential interference by the secondary users. By using a MAC
protocol with one-slot memory, we can obtain high channel utilization by the
secondary users while limiting interference to the primary user at a low level.
The results of this paper suggest the possibility of utilizing MAC design in
cognitive radio networks to overcome limitations in spectrum sensing at the PHY
layer as well as to achieve spectrum sharing at the MAC layer.Comment: 24 pages, 7 figure
Adaptive MAC Protocols Using Memory for Networks with Critical Traffic
We consider wireless communication networks where network users are subject
to critical events such as emergencies and crises. If a critical event occurs
to a user, the user needs to send critical traffic as early as possible.
However, most existing medium access control (MAC) protocols are not adequate
to meet the urgent need for data transmission by users with critical traffic.
In this paper, we devise a class of distributed MAC protocols that achieve
coordination using the finite-length memory of users containing their own
observations and traffic types. We formulate a protocol design problem and find
optimal protocols that solve the problem. We show that the proposed protocols
enable a user with critical traffic to transmit its critical traffic without
interruption from other users after a short delay while allowing users to share
the channel efficiently when there is no critical traffic. Moreover, the
proposed protocols require short memory and can be implemented without explicit
message passing.Comment: 24 pages, 7 figures, 1 tabl